The present invention relates to an electrostatographic printing method for forming a plurality of duplicated copies of an original comprising a step for forming a primary electrostatic charge latent image corresponding to an image of the original on a photosensitive member including photoconductive material; a step for developing the latent image with a toner development agent to form a primary toner image; a step for fixing the primary toner image to form a printing master; and a step for forming a plurality of copies with the aid of the printing master in an electrophotographic manner.
The present invention also relates to an apparatus for forming such a printing master and an apparatus for printing a plurality of copies with the aid of the printing master.
Heretofore there have been proposed various methods for printing a number of duplicated copies by an electrophotographic process or printing process on the basis of the same and signal master image once formed by a single exposure step. For instance in U.S. Pat. No. 2,951,443, No. 3,363,555, No. 3,598,580 and No. 3,627,523 there is disclosed a method for forming a plurality of duplicated copies by a single electrostatic charge latent image once formed on a photoconductive member is repeatedly developed with toner particles and each toner image is transferred onto a paper without deteriorating the latent image. In a Japanese Patent Publication No. 20,347/65 there is described another printing method wherein a photosensitive member on which a toner developed image has been formed is subjected to strong light to form a master image composed of persistent conductivity pattern, and a plurality of copies are formed by subjecting repeatedly the master image to well known electrophotographic processes. Further in a Japanese Patent Publication No. 42,469/71 there is disclosed a printing method in which a high resistive resin layer is selectively formed on a toner image which has been formed on a photosensitive member and after that the photosensitive layer is exposed to strong light to form a master image composed of persistent conductivity pattern corresponding to the toner image. In another method described in a Japanese Patent Laid-Open Publication No. 34,836/74 a toner image which has been formed by an electrophotographic process is transferred onto a conductive sheet to form a master image. In a Japanese Patent Publication No. 23,288/73 there is disclosed still another method wherein a photosensitive member having a toner image formed thereon is subjected to a heating process so as to break thermally a non-pictorial area of the member to form a printing master. In Japanese Patent Laid-Open Publication No. 8,730/72 (corresponding to U.S. Patent Application Ser. No. 81,212 filed on Oct. 16, 1970) there is described another method in which an electrostatic latent image formed on a photosensitive member is developed with toner particles, the toner image thus formed is transferred onto a web while a part of the toner image being remained on the photosensitive member, the electrostatic latent image is enhanced by effecting uniform charging and exposing steps, the enhanced latent image is developed with toners, the toner image thus formed is partially transferred to an image receiving member and the above steps are successively repeated to form a number of duplicated copies. Further in the Japanese Laid-Open Publication No. 39,044/76 there is described a method wherein a toner image is formed on a transparent photosensitive member to form a printing master. In a Japanese Patent Publication No. 21,095/65 still another known method is disclosed in which use is made of a master which has been formed by an electrically insulating toner image on a photosensitive member, an electrostatic charge latent image is formed on the toner image by effecting uniform charging and exposing steps, the latent image thus formed is developed by a liquid development step and only the toner image formed by the liquid development is transferred onto a record paper.
In the known methods in which a master image is composed of persistent conductivity pattern the persistent conductivity is liable to be deteriorated depending on the number of copies and thus the maximum number of copies is limited. Since in another known methods special photosensitive material, toners and surface coatings have to be used the processes are complicated and thus become expensive. Under the circumstances in a practically used multi-copying method a toner image is formed on a zinc oxide paper by liquid or dry toner development and is then fixed thereon, a non-pictorial area is made insensitive to oily paint or a pictorial area is made sensitive to oily paint to form a master image and a number of copies are formed by off-set printing with the aid of the master. However in this known method oily paint having high viscosity might stain the apparatus and the operation is liable to be critical as compared with general copying machines. Moreover if the printing apparatus is made automized, the whole apparatus becomes quite large in size.